Streamline OperationHandler API in TypeScript

[elmerbulthuis]

currently, a typical operation handler looks something like this:

export function createDummyOperationHandler
  context: application.Context,
): api.DummyOperationHandler<{}> {
  return async (incomingRequest, authentication, accept) => {
    const entity = await incomingRequest.entity();
    // do someting
    return {
      status: 200,
      parameters: {},
      contentType: "application/json",
      entity() {
        return entity;
      }
    };
  };
}

This is quite a lot of boilerplate! We want to clean this up. Especially this part:

    return {
      status: 200,
      parameters: {},
      contentType: "application/json",
      entity() {
        return entity;
      }

The status, could be optionally if there is only one 2xx response. This is then the default. Also this could be a string that is the name of a well known status. Then if there are no parameters or if all parameters are optional we can omit the parameters.

So something like this:

    return {
      contentType: "application/json",
      entity() {
        return entity;
      }

Then, we should have a default content-type. This is usually the first in a list of request types. If there is only one then this is the default. Finally the entity member should be a property. If we apply that as well we get:

    return {
      entity,
   }

The entire handler would look something like thid:

export function createDummyOperationHandler
  context: application.Context,
): api.DummyOperationHandler<{}> {
  return async (incomingRequest, authentication, accept) => {
    const entity = await incomingRequest.entity();
    // do someting
    return { entity };
  };
}